Solid-state imaging device and method of manufacturing solid-state imaging device

ABSTRACT

A solid state imaging device having a back-illuminated type structure in which a lens is formed on the back side of a silicon layer with a light-receiving sensor portion being formed thereon. Insulating layers are buried into the silicon layer around an image pickup region, with the insulating layer being buried around a contact layer that connects an electrode layer of a pad portion and an interconnection layer of the surface side. A method of manufacturing such a solid-state imaging device is also provided.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation Application of the patentapplication Ser. No. 11/723,241, filed Mar. 19, 2007, which is based onpatent application Ser. No.: 11/441,112, filed May 26, 2006, which isbased on Parent application Ser. No.: 10/979,116, filed Nov. 3, 2004,now U.S. Pat. No. 7,101,726, issued Sep. 5, 2006, which in turn claimspriority from Japanese applications No. 2003-386933 filed on Nov. 17,2003, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a solid-state imaging device having aso-called back-illuminated structure for illuminating light on alight-receiving sensor portion from the back side opposite to electrodesand interconnections and a method of manufacturing such aback-illuminated type solid-state imaging device.

2. Description of the Related Art

It has been customary that a solid-state imaging device has asurface-illuminated type structure with electrodes and interconnectionsformed on a substrate to illuminate light on a light-receiving sensorportion from above the electrodes and the interconnections.

FIG. 1 of the accompanying drawings is a schematic cross-sectional viewshowing a solid-state imaging device having a surface-illuminated typestructure.

A solid-state imaging device, generally depicted by the referencenumeral 50 in FIG. 1, is a CMOS (complementary metal-oxidesemiconductor) solid-state imaging device having a surface illuminatedtype structure.

As shown in FIG. 1, a photodiode PD comprising a light-receiving sensorportion of each pixel is formed within a silicon substrate 51, and aninterconnection layer 53 of a multi-layer is formed on the siliconsubstrate 51 through an interlayer insulator 52. Further, a color filter54 and a lens 55 are formed on the layer above the interconnection layer53.

Light L is passed from the lens 55 through the interlayer insulator 52between the color filter 54 and the interconnection layer 53 andintroduced into the photodiode PD of the light-receiving sensor portion.

However, as the solid-state imaging device is microminiaturizedincreasingly, the pitch of interconnection becomes narrower and theinterconnection layer 53 is formed of many more layers so that adistance between the lens 55 and the photodiode PD of thelight-receiving sensor portion is increased unavoidably.

As a consequence, as shown hatched in FIG. 1, a part Lx of the light L,which became incident on the solid-state imaging device 50 obliquely, isinterrupted by the interconnection layer 53 and cannot be introducedinto the photodiode PD, thereby causing a bad phenomenon such as shadingto occur.

As a plan for improving the above bad phenomenon, a back-illuminatedtype solid-state imaging device has been proposed to illuminate light ona light-receiving sensor portion from the opposite side of the surfaceon which interconnections are formed (for example, see Cited patentreference 1).

While the cited patent reference 1 has described a CCD (charge-coupleddevice) solid-state imaging device having a back-illuminated typestructure, it is considered that this back-illuminated type structurecan be applied to the CMOS type solid-state imaging device.

FIG. 2 is a schematic cross-sectional view showing an example of a CMOStype solid-state imaging device with a back-illuminated type structurebeing applied thereto.

As shown in FIG. 2, a photodiode PD comprising a light-receiving sensorportion of each pixel is formed within a single crystal silicon layer61, and a color filter 64 and a lens 65 are formed on the single crystalsilicon layer 61. The single crystal silicon layer 61 is formed of asilicon substrate whose thickness is reduced, as will be described lateron.

On the other hand, a multilayer interconnection layer 63 is formed underthe single crystal silicon layer 61 through an interlayer insulator 62,and the interlayer insulator 62 in which the interconnection layer 63 isformed is supported by a supporting substrate 66 formed under theinterconnection layer 63.

Then, light L is introduced from the lens 65 into the photodiode PD ofthe light-receiving sensor portion formed on the single crystal siliconlayer 61.

Assuming that the side in which the interconnection layer 63 is formedis the surface side, the light L is introduced into the photodiode PDfrom the back side. Thus, this structure of the above CMOS typesolid-state imaging device is referred to as a “back-illuminated typestructure”.

In the back-illuminated type solid-state imaging device like thesolid-state imaging device 60 shown in FIG. 2, the incident light is notinterrupted by the interconnection layer 63 so that an effectivevignetting factor relative to oblique incident light can reach 100%.

Accordingly, it can be expected much that sensitivity of thisback-illuminated type solid-state imaging device can be improvedconsiderably and that this back-illuminated type solid-state imagingdevice will be free from the shading.

The solid-state imaging device 60 shown in FIG. 2 can be manufactured asfollows.

First, the photodiode PD 60 comprising the light-receiving sensorportion is formed near the surface of a silicon substrate 71 by asuitable method such as ion implantation. Then, an interconnection layer63A of a first layer is formed on the silicon substrate 71 through agate insulating film 72 and the interconnection layer 63 following thesecond layer is formed through the interlayer insulator 62, in thatorder (see FIG. 3A).

Then, as shown in FIG. 3B, an SiO₂ layer 73 is deposited on the surfaceof the insulating layer 62 and the surface thereof is polished. At thesame time, a silicon substrate is prepared as the supporting substrate66 and an SiO₂ layer 74 is formed on the surface of the supportingsubstrate 66. These SiO₂ layers 73, 74 are bonded together in anopposing fashion.

Subsequently, as shown in FIG. 3C, the resultant product is inverted upand down so that the side of the supporting substrate 66 may be directedto the lower direction.

Next, as shown in FIG. 3D, the silicon substrate 71 is reduced inthickness by polishing the surface of the silicon substrate 71 andthereby the single crystal silicon layer 61 in which the photodiode PDis formed and which has a predetermined thickness is obtained.

Next, as shown in FIG. 3E, the color filter 64 and the lens 65 areformed on the single crystal silicon layer 61 through a planarized layer75 (not shown in FIG. 2).

Thereafter, the supporting substrate 66 is reduced in thicknessaccording to the need.

In this manner, it is possible to manufacture the solid-state imagingdevice 60 shown in FIG. 2.

[Cited patent reference 1]: Official gazette of Japanese laid-openpatent application No. 6-283702 (FIGS. 5A, 5B) While the lens 65 isformed on the single crystal silicon layer 61 in the final process (FIG.3E) of the manufacturing processes shown in FIGS. 3A to 3E, at thattime, the lens 65 has to be formed in alignment with the photodiode PDthat has already been formed so that an alignment mark is indispensableto such final process (FIG. 3E).

However, in the structure of the back-illuminated type solid-stateimaging device according to the related art, it has not been consideredso far to form an alignment mark.

Also, in the back-illuminated type solid-state imaging device, since thelens is formed on the back side of the silicon substrate, it is notpossible to manufacture the alignment mark of the lens relative to thephotodiode by a method similar to the alignment mark producing method inthe surface-illuminated type solid-state imaging device (method offorming the alignment mark on the surface of the silicon substrate).

Also, similarly, since the supporting substrate and the like areattached to the side of the interconnection layer, it is impossible toform a pad contact by an ordinary method.

For this reason, the alignment mark forming method and the pad contactforming method should be established. Otherwise, it becomes impossibleto realize a back-illuminated type solid-state imaging device, and henceit becomes difficult to microminiaturize the solid-state imaging deviceand to improve performance such as resolution.

That is, in order to realize the back-illuminated type solid-stateimaging device, there are required an alignment mark forming method forforming an alignment mark on a silicon substrate in order to align thephotodiode and the lens and a pad contact forming method.

SUMMARY OF THE INVENTION

In view of the aforesaid aspect, it is an object of the presentinvention to provide a solid-state imaging device which can realize aback-illuminated type solid-state imaging device by forming an alignmentmark for precisely aligning a photodiode of a light-receiving sensorportion and a lens and a pad contact to the back-illuminated typesolid-state imaging device and a method of manufacturing a solid-stateimaging device.

According to an aspect of the present invention, there is provided asolid-state imaging device including a structure comprising at least asilicon layer in which a light-receiving sensor portion for effectingphotoelectric-conversion is formed, an interconnection layer formed onthe surface side of this silicon layer and in which a lens is formed onthe rear side opposite to the surface side of the silicon layer, aninsulating layer being buried into the silicon layer around an imagepickup region, the insulating layer being buried around a contact layerfor connecting an electrode layer of a pad portion and theinterconnection layer of the surface side.

According to the above-mentioned arrangement of the solid-state imagingdevice of the present invention, since this solid-state imaging deviceincludes the structure comprising at least the silicon layer in whichthe light-receiving sensor portion for effectingphotoelectric-conversion is formed and the interconnection layer formedon the surface side of this silicon layer and in which the lens isformed on the rear side opposite to the surface side of the siliconlayer, the solid-state imaging device having the so-calledback-illuminated type structure is constructed in which the lens isformed on the rear side opposite to the surface side of the siliconlayer.

Then, since the insulating layer is buried into the silicon layer aroundthe image pickup region, when the solid-state imaging device ismanufactured, it becomes possible to align the light-receiving sensorportion and the lens by using this insulating layer as the alignmentmark.

Also, since the insulating layer is buried around the contact layer forconnecting the electrode layer of the pad portion and theinterconnection layer of the surface side, the contact layer and thesilicon layer can be insulated from each other by the insulating layerand the pad portion can be constructed by connecting the electrode layerto the interconnection layer of the surface side through the contactlayer.

According to other aspect of the present invention, there is provided asolid-state imaging device including a structure comprising at least afirst silicon layer in which a light-receiving sensor portion foreffecting photoelectric-conversion is formed and which is formed of asingle crystal silicon layer, an interconnection layer formed on thesurface side of this first silicon layer and in which a lens is formedon the rear side opposite to the surface side of the first siliconlayer, a second silicon layer formed of an amorphous silicon layer or apolycrystalline silicon layer is buried into the first silicon layeraround an image pickup region, an insulating layer is formed on thefirst silicon layer, a metal layer is buried into the insulating layerat its portion above the second silicon layer, the insulating layer isburied around a contact layer for connecting an electrode layer of a padportion and an interconnection layer of the surface side and the secondsilicon layer is buried around the insulating layer.

According to the above-mentioned arrangement of the solid-state imagingdevice of the present invention, since this solid-state imaging devicehas the structure comprising at least the first silicon layer in whichthe light-receiving sensor portion for effectingphotoelectric-conversion is formed and the interconnection layer formedon the surface side of the first silicon layer and in which the lens isformed on the rear side opposite to the surface side of the firstsilicon layer, the solid-state imaging device having the so-calledback-illuminated type structure is constructed in which the lens isformed on the back side opposite to the surface side of the firstsilicon layer.

Then, since the second silicon layer formed of the amorphous siliconlayer or the polycrystalline silicon layer is buried into the firstsilicon layer around the image pickup region, the insulating layer isformed on the first silicon layer and the metal layer is buried into theinsulating layer at its portion above the second silicon layer, when thesolid-state imaging device is manufactured, it becomes possible to alignthe light-receiving sensor portion and the lens by using this metallayer as the alignment mark.

Also, since the insulating layer that is formed on the first siliconlayer is buried around the contact layer for connecting the electrodelayer of the pad portion and the interconnection layer of the surfaceside and the second silicon layer is buried around the insulating layer,the contact layer, the second silicon layer and the first silicon layercan be insulated from one another by the insulating layer, and the padportion can be constructed by connecting the electrode layer to theinterconnection layer of the surface side through the contact layer.

According to a further aspect of the present invention, a method ofmanufacturing a solid-state imaging device is a method of manufacturinga solid-state imaging device for manufacturing a solid-state imagingdevice including a structure comprising a silicon layer in which alight-receiving sensor portion for effecting photoelectric-conversion isformed and an interconnection layer formed on the surface side of thissilicon layer and in which a lens is formed on the back side opposite tothe surface side of the silicon layer. This method of manufacturing asolid-state imaging device comprises a process for forming a groove on asilicon layer around an image pickup region, a process for forming agroove on a silicon layer of a pad portion, a process for burying aninsulating layer into the groove formed around the image pickup region,a process for burying the insulating layer into the groove formed on thepad portion, a process for forming the light-receiving sensor portion onthe silicon layer after the insulating layer was buried around at leastthe image pickup region, a process for forming an interconnection layeron the surface side of the silicon layer, a process for connecting anelectrode layer to the interconnection layer of the pad portion byburying a conductive material into the insulating layer buried into thegroove of the pad portion and a process for forming a lens on the rearside of the silicon layer by using the insulating layer buried into thegroove around the image pickup region as an alignment mark.

According to the above-mentioned method of manufacturing a solid-stateimaging device of the present invention, there can be manufactured thesolid-state imaging device including the structure comprising at leastthe silicon layer in which the light-receiving sensor portion foreffecting photoelectric-conversion is formed and the interconnectionlayer formed on the surface side of this silicon layer and in which thelens is formed on the rear side opposite to the surface side of thesilicon layer, that is, the solid-state imaging device having theso-called back-illuminated type structure.

Then, according to the above-mentioned method of manufacturing asolid-state imaging device of the present invention, since thismanufacturing method comprises the process for forming the groove on thesilicon layer around the image pickup region, the process for buryingthe insulating layer into the groove formed around the image pickupregion, the process for forming the interconnection layer on the surfaceside of the silicon layer, the process for forming the light-receivingsensor portion on the silicon layer after the insulating layer wasburied around at least the image pickup region and the process forforming the lens on the rear side of the silicon layer by using theinsulating layer buried into the groove around the image pickup regionas the alignment mark, it becomes possible to form the photodiode of thelight-receiving sensor portion at the accurate position by using theinsulating layer as the alignment mark and further it becomes possibleto align the lens at the accurate position relative to the photodiode ofthe light-receiving sensor portion and the like.

Also, according to the present invention, this method of manufacturing asolid-state imaging device comprises the process for forming the grooveon the silicon layer of the pad portion, the process for burying theinsulating layer into the groove formed at the pad portion and theprocess for connecting the electrode layer to the interconnection layerof the pad portion by burying the conductive material into theinsulating layer buried into the groove of the pad portion, theconductive material buried into the insulating layer is connected to theinterconnection layer of the pad portion and the conductive material andthe silicon layer are insulated from each other by the insulating layer.Thus, the pad electrode is formed by using the conductive material asthe contact layer, thereby making it possible to form the pad portion.

According to the above-mentioned method of manufacturing a solid-stateimaging device of the present invention, in the process for forming thegroove on the silicon layer around the image pickup region, the siliconlayer may be etched by using a silicon nitride layer as a mask, asilicon oxide layer may be buried into the groove as the insulatinglayer in the state in which the silicon nitride layer is left and thesilicon oxide layer may be left only within the groove by removing thesilicon oxide layer from the surface, whereafter the silicon oxide layermay be protruded on the surface by removing the silicon nitride layerand the light-receiving sensor portion may be formed on the siliconlayer.

In this case, it becomes possible to form the photodiode of thelight-receiving sensor portion and the like at the predeterminedposition by using the protruded silicon oxide layer as the alignmentmark.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, it is possible to execute theprocess for forming the groove on the silicon layer around the imagepickup region and the process for forming the groove on the siliconlayer of the pad portion at the same time. Also, the process for buryingthe insulating layer into the groove formed around the image pickupregion and the process for burying the insulating layer into the grooveformed on the pad portion can be executed at the same time.

In this case, since the groove forming process and the process forburying the insulating layer into the groove are simultaneously aroundthe image pickup region and the pad portion, it becomes possible todecrease the number of processes.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, it is further possible toseparately execute the process for forming the groove on the siliconlayer around the image pickup region, the process for burying theinsulating layer into the groove formed around the image pickup region,the process for forming the groove on the silicon layer of the padportion and the process for burying the insulating layer into the grooveformed on the pad portion.

In this case, since the groove forming process and the process forburying the insulating layer into the groove are separately executedaround the image pickup region and at the pad portion, it becomespossible to optimize the material of the insulating layer buried intothe groove and the method of forming the groove in consideration ofvarious characteristics such as a burying property and an etching rate.

Furthermore, after the insulating layer was buried into the grooveformed around the image pickup region, the process for forming thelight-receiving sensor portion on the silicon layer can be executed,whereafter the groove can be formed on the silicon layer of the padportion and the insulating layer can be buried into this groove. In thiscase, it is possible to form the photodiode of the light-receivingsensor portion and the like with high accuracy by using the insulatinglayer buried into the groove formed around the image pickup region asthe alignment mark. Also, since the insulating layer buried into thegroove of the pad portion is not used as the alignment mark, thematerial of the insulating layer can be selected freely.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, further, a second groovenarrower than the width of the insulating layer and which reaches theinterconnection layer of the pad portion through the insulating layercan be formed on the insulating layer buried into the groove of the padportion, a third groove narrower than the width of the insulating layerand which is wider than the width of the second groove can be formed onthe upper portion of the second groove and then the electrode layer canbe connected to the interconnection layer of the pad portion by buryingthe conductive material into the second and third grooves.

In this case, the conductive material within the narrow second groovecan act as the contact layer and it becomes possible to use theconductive material buried into the wider third groove formed on theupper portion of the second groove as the pad electrode. As a result,the contact layer and the pad electrode can be formed at the same time.

A method of manufacturing a solid-state imaging device according to thepresent invention is a method of manufacturing a solid-state imagingdevice including a structure comprising at least a first silicon layerin which a light-receiving sensor portion for effectingphotoelectric-conversion is formed, an interconnection layer formed onthe surface side of this first silicon layer and a lens formed on therear side opposite to the surface side of the first silicon layer. Thissolid-state imaging device manufacturing method comprises a process forforming a groove on a first silicon layer around an image pickup region,a process for forming a groove on the first silicon layer of a padportion, a process for burying a second silicon layer made of amorphoussilicon or polycrystalline silicon into a groove formed around the imagepickup region, a process for burying the second silicon layer made ofamorphous silicon or polycrystalline silicon into the groove formed atthe pad portion, a process for forming a light-receiving sensor portionon the first silicon layer after the second silicon layer was buriedaround at least the image pickup region, a process for forming aninterconnection layer on the surface side of the first silicon layer, aprocess for connecting an electrode layer to the interconnection layerby burying a conductive material into the second silicon layer buriedinto the groove of the pad portion through an insulating layer and aprocess for forming the insulating layer over the first silicon layer,burying a metal layer into the insulating layer at its portion above thesecond silicon layer around the image pickup region and forming a lenson the back side of the first silicon layer by using this metal layer asan alignment mark.

The above-mentioned method of manufacturing a solid-state imaging deviceaccording to the present invention is to manufacture a solid-stateimaging device including a structure comprising at least a first siliconlayer in which a light-receiving sensor portion for effectingphotoelectric-conversion is formed, an interconnection layer formed onthe surface side of this first silicon layer and a lens formed on therear side opposite to the surface side of the first silicon layer, thatis, a solid-state imaging device having a so-called back-illuminatedtype structure.

Then, according to the above-mentioned method of manufacturing asolid-state imaging device of the present invention, since thissolid-state imaging device manufacturing method comprises the processfor forming the groove on the first silicon layer around the imagepickup region, the process for burying the second silicon layer made ofthe amorphous silicon or polycrystalline silicon into the groove formedaround the image pickup region, the process for forming thelight-receiving sensor portion on the first silicon layer after thesecond silicon layer was buried around at least the image pickup region,the process for forming the interconnection layer on the surface side ofthe first silicon layer and the process for forming the insulating layerover the first silicon layer, burying the metal layer into theinsulating layer at its portion above the second silicon layer aroundthe image pickup region and forming the lens on the rear side of thefirst silicon layer by using this metal layer as the alignment mark, itbecomes possible to accurately align the photodiode of thelight-receiving sensor portion and the like at the predeterminedposition by using the second silicon layer around the image pickupregion as the alignment mark. Further, it becomes possible to form thelens with the accurate alignment relative to the photodiode of thelight-receiving sensor portion and the like by using the metal layerformed on the portion above the second silicon layer around the imagepickup region as the alignment mark.

Also, since the solid-state imaging device manufacturing methodaccording to the present invention comprises the process for forming thegroove on the first silicon layer of the pad portion, the process forburying the second silicon layer made of the amorphous silicon or thepolycrystalline silicon into the groove formed on the pad portion andthe process for connecting the conductive material to theinterconnection layer by burying the conductive material into the secondsilicon layer buried into the groove of the pad portion through theinsulating layer, the conductive material buried into the second siliconlayer through the insulating layer is connected to the interconnectionlayer of the pad portion and the conductive material and the secondsilicon layer are insulated from each other by the insulating layer. Inconsequence, the pad electrode can be formed by using the conductivematerial as the contact layer, thereby making it possible to form thepad portion.

In the above-mentioned method of manufacturing a solid state imagepickup device according to the present invention, further, the processfor forming the groove on the first silicon layer around the imagepickup region and the process for forming the groove on the firstsilicon layer of the pad portion can be executed at the same time. Also,the process for burying the second silicon layer into the groove formedaround the image pickup region and the process for burying the secondsilicon layer into the groove formed at the pad portion can be executedat the same time.

In this case, since the groove forming process and the process forburying the second silicon layer into the groove are executed around theimage pickup region and at the pad portion at the same time, it becomespossible to decrease the number of the processes.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, further, the process forforming the first silicon layer around the image pickup region and theprocess for burying the second silicon layer into the groove formedaround the image pickup region; and the process for forming the grooveon the first silicon layer of the pad portion and the process forburying the second silicon layer into the groove formed at the padportion can be executed separately.

In this case, since the groove forming process and the process forburying the second silicon layer into the groove are executed around theimage pickup region and at the pad portion separately, it becomespossible to optimize the material (amorphous silicon or polycrystallinesilicon) of the second silicon layer buried into the groove and theforming method in consideration of various characteristics such as aburying property and an etching rate.

Further, after the second silicon layer was buried into the grooveformed around the image pickup region, the light-receiving sensorportion can be formed on the first silicon layer, whereafter the groovecan be formed on the first silicon layer of the pad portion and thesecond silicon layer can be buried into this groove. In this case, itbecomes possible to form the photodiode of the light-receiving sensorportion and the like accurately by using the second silicon layer buriedinto the groove formed around the image pickup region as the alignmentmark. Also, since the second silicon layer buried into the groove of thepad portion is not used as the alignment mark, the material can beselected freely.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, further in the process forforming the groove on the first silicon layer around the image pickupregion, the first silicon layer may be etched by using the insulatinglayer as a mask, the second silicon layer may be buried into the groovein the state in which the insulating layer is left, the second siliconlayer may be left only within the groove by removing the second siliconlayer from the surface, the second silicon layer may be protruded on thesurface by removing the insulating layer and the light-receiving sensorportion may be formed on the first silicon layer.

In this case, it becomes possible to form the photodiode of thelight-receiving sensor portion and the like at the predeterminedposition by using the thus protruded second silicon layer as thealignment mark.

According to the above-mentioned present invention, it becomes possibleto align the light-receiving sensor portion (photodiode, etc.) and thelens by using the insulating layer buried into the groove around theimage pickup region or the second silicon layer buried into the groovearound the image pickup region and the metal layer formed on the secondsilicon layer as the alignment mark.

In consequence, also in the solid-state imaging device having theback-illuminated type structure, it becomes possible to align thelight-receiving sensor portion (photodiode, etc.) and the lens at thepredetermined position accurately.

Further, according to the present invention, it becomes possible to forma pad by connecting the electrode layer and the interconnection layerafter the contact layer was formed by connecting the interconnectionlayer formed on the surface side in the pad portion.

Thus, it becomes possible to form the pad in the solid-state imagingdevice having the back-illuminated type structure too.

Therefore, according to the present invention, it becomes possible torealize the solid-state imaging device having the back-illuminated typestructure. Also, it becomes possible to achieve an effective vignettingfactor of 100% of slanting incident light by the back-illuminated typestructure. Further, it becomes possible to considerably improvesensitivity and to realize the solid-state imaging device having theback-illuminated type structure which is free from the shading.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing a CMOS type solid-state imagingdevice having a surface-illuminated type structure;

FIG. 2 is a cross-sectional view showing a CMOS type solid-state imagingdevice having a back-illuminated type structure;

FIGS. 3A to 3E are process diagrams used to explain a method ofmanufacturing a CMOS type solid-state imaging device having aback-illuminated type structure, respectively;

FIG. 4 is a schematic cross-sectional view showing an arrangement of asolid-state imaging device according to an embodiment of the presentinvention;

FIGS. 5A and 5B are schematic diagrams to which reference will be madein explaining the position of an alignment mark, respectively;

FIGS. 6A to 6C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 7A to 7C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 8A to 8C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 9A to 9C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 10A to 10C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 11A to 11C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 12A to 12C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 13A to 13C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 14A to 14C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 15A to 15C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 16A and 16B are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 17A to 17C are process diagrams used to explain other example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 18A to 18C are process diagrams used to explain other example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 19A to 19C are process diagrams used to explain other example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 20A to 20C are process diagrams used to explain other example of amethod of manufacturing a solid-state imaging device shown in FIG. 4,respectively;

FIGS. 21A to 21C are process diagrams used to explain a further exampleof a method of manufacturing a solid-state imaging device shown in FIG.4, respectively;

FIGS. 22A to 22C are process diagrams used to explain a further exampleof a method of manufacturing a solid-state imaging device shown in FIG.4, respectively;

FIGS. 23A to 23C are process diagrams used to explain a further exampleof a method of manufacturing a solid-state imaging device shown in FIG.4, respectively;

FIGS. 24A to 24C are process diagrams used to explain a further exampleof a method of manufacturing a solid-state imaging device shown in FIG.4, respectively;

FIGS. 25A and 25B are process diagrams used to explain a further exampleof a method of manufacturing a solid-state imaging device shown in FIG.4, respectively;

FIG. 26 is a schematic cross-sectional view showing an arrangement of asolid-state imaging device according to other embodiment of the presentinvention;

FIGS. 27A to 27C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 26,respectively;

FIGS. 28A to 28C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 26,respectively;

FIGS. 29A and 29B are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 26,respectively;

FIGS. 30A to 30C are process diagrams used to explain yet a furtherexample of a solid-state imaging device shown in FIG. 4, respectively;

FIGS. 31A and 31B are process diagrams used to explain yet a furtherexample of a solid-state imaging device shown in FIG. 4, respectively;

FIG. 32 is a schematic cross-sectional view showing an arrangement of asolid-state imaging device according to a further embodiment of thepresent invention;

FIGS. 33A to 33C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 32,respectively;

FIGS. 34A to 34C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 32,respectively;

FIGS. 35A to 35C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 32,respectively; and

FIGS. 36A to 36C are process diagrams used to explain an example of amethod of manufacturing a solid-state imaging device shown in FIG. 32,respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail with reference tothe drawings.

FIG. 4 is a schematic diagram (cross-sectional view) showing anarrangement of a solid-state imaging device according to an embodimentof the present invention.

In this embodiment, the present invention is applied to a CMOS typesolid-state imaging device having a back-illuminated type structure.

As shown in FIG. 4, a solid-state imaging device 1 includes a siliconlayer 2 in which a photodiode PD serving as a light-receiving sensorportion is formed. A color filter 6 is formed on the silicon layer 2through a planarized layer 5 and an on-chip lens 7 is formed on thecolor filter 6. Also, an interconnection portion in whichinterconnection layers 4 of a plurality of layers (three layers in FIG.4) are formed within an insulating layer 3 is formed under the siliconlayer 2. The interconnection portion is formed on a supporting substrate8 and the whole of this solid-state imaging device is supported by thissupporting substrate 8.

As shown in FIG. 4, the color filter 6 and the on-chip lens 7 aredisposed on the opposite side of the surface side of the silicon layer 2in which the light-receiving sensor portion (photodiode PD) is formed,that is, on the back side of the silicon layer 2, thereby forming thesolid-state imaging device 1 having the back-illuminated type structure.

The insulating layer 3 of the interconnection portion and the supportingsubstrate 8 are bonded and fixed by adhesive layers 9, 10. When thesupporting substrate 8 is formed of a silicon substrate, for example,the adhesive layers 9, 10 can be formed of SiO₂ films.

Further, as shown in FIG. 4, an insulating layer (for example, an SiO₂layer) 13 serving as an alignment mark is formed around an image pickupregion 20 such that it may be extended through the silicon layer 2 so asto partly overlap the upper portion of the insulating layer 3 formedunder the silicon layer 2.

Outside the image pickup region 20, an electrode layer 15 formed on thesurface is connected to an interconnection layer 11 formed of the samelayer as that of the interconnection layer 4 of the uppermost layerthrough a contact layer 12 formed through the silicon layer 2 and theupper portion of the insulating layer 3 to thereby construct a padportion. The contact layer 12 is insulated from the silicon layer 2 byan insulating layer (for example, SiO₂ layer) 14.

The insulating layer 13 serving as the alignment mark has a differentreflectivity relative to the silicon layer 2 and hence it can be used asthe alignment mark. For example, the position of the insulating layer 13can be detected with illumination of light from above.

Also, the insulating layer 13 and the insulating layer 14 of the padportion are composed of insulating layers of the same material formed atthe same time.

When the solid-state imaging device 1 shown in FIG. 4 is manufactured, alarge number of chips 101 of the solid-state imaging device 1 are formedwithin a wafer 100 as shown in a plan view of FIG. 5A.

FIG. 5B is a schematic plan view showing the wafer 100 shown in FIG. 5Ain an enlarged-scale. As shown in FIG. 5B, the insulating layers 13serving as the alignment marks of the predetermined number are locatedat the predetermined positions outside the image pickup region 20 ineach chip 101.

The arrangement of the alignment marks on the plane is not limited tothe arrangement shown in FIG. 5B and other arrangements of the alignmentmarks also are possible.

The solid-state imaging device 1 according to this embodiment can bemanufactured as follows, for example.

First, as shown in FIG. 6A, a thin oxide film 22 is formed by oxidizingthe surface of a silicon substrate 21.

Next, as shown in FIG. 6B, an SiN film (silicon nitride layer) 23 and aphotoresist 24 are deposited on the oxide film 22, in that order.

Next, as shown in FIG. 6C, a through-hole is formed by exposing anddeveloping the photoresist 24.

Next, as shown in FIG. 7A, the SiN film 23 is etched by using thephotoresist 24 as a mask and thereby a through-hole is formed on the SiNfilm 23. Further, as shown in FIG. 7B, the SiN film 23 is left byremoving the photoresist 24, thereby forming a hard mask (SiN film 23)for etching the silicon substrate 21.

Next, as shown in FIG. 7C, an alignment mark groove and a pad contacthole having depths ranging from 5 to 20 μm are formed on the siliconsubstrate 21 by an RIE (reactive ion etching) method. The depths of thealignment mark groove and the pad contact hole are made corresponding tothe depth of a photodiode PD which will be formed later on.

Next, as shown in FIG. 8A, an insulating layer 25 made of SiO₂, forexample, is deposited on the whole surface so as to fill the grooveformed on the silicon substrate 21. The material of the insulating layer25 to be filled may be a suitable material such as SiN and theinsulating layer 25 may be made of any material so long as the materialis an insulating material.

Next, the insulating layer 25 is removed from the surface by a CMP(chemical mechanical polish) method or an RIE method, whereby theinsulating layer 25 is left only in the groove and the contact hole asshown in FIG. 8B.

Subsequently, the SiN film 23 is removed and an impurity regioncomprising the photodiode PD of the light-receiving sensor portion isformed within the silicon layer 21 as shown in FIG. 8C. At that time,since the insulating layer 25 buried into the portion corresponding tothe peripheral portion of the image pickup region 20 has a reflectivitydifferent from that of the surrounding silicon layer 21 and the surfaceof the insulating layer 25 is protruded, the photodiode PD can bealigned by using this insulating layer 25.

Next, as shown in FIG. 9A, the interconnection layers 4 of multilayerare sequentially formed on the silicon substrate 21 through theinsulating layer 4 and thereby an interconnection portion is formed.

After that, an SiO₂ film (adhesive layer) 9 is formed on the surface ofthe insulating layer 3 and the surface of the insulating layer 3 isplanarized and polished. At the same time, a supporting substrate 8 witha T-SiO₂ film (adhesive layer) 9 formed on the surface thereof isprepared and the insulating layer 3 of the interconnection portion andthe supporting substrate 8 are bonded together as shown in FIGS. 9B and9C in such a manner that the SiO₂ films 9, 10 may be opposed to eachother as shown in FIG. 9B.

Next, the wafer is inverted as shown in FIG. 10A.

Next, the silicon substrate 21 that is the wafer rear material isdecreased in thickness by the CMP method, the RIE method or a BGR(background) method or a combination of these three methods such that atleast the insulating layers 25 formed within the previously-formedgroove and the contact hole may be exposed as shown in FIG. 10B. As aconsequence, the silicon layer 2 is formed from the silicon substrate 21and the insulating layer 13 of the alignment mark is formed from theinsulating layer 25. Also, the insulating layer 25 of the pad portion isformed as the insulating layer 14 around the contact layer 12.

If the depth of the groove formed on the silicon substrate 21 is set inresponse to the thickness of the final silicon layer 2, then it becomespossible to use the insulating layer 25 buried into the groove as thelayer to detect the end required when the silicon substrate 21 isdecreased in thickness.

Subsequently, the contact of the pad portion is formed.

First, a photoresist 26 is formed on the surface and the photoresist 26is exposed and developed and thereby formed as a mask having athrough-hole at the pad portion as shown in FIG. 10C. At that time, thesize of the through-hole is made smaller than the insulating layer 25 ofthe pad portion.

Next, as shown in FIG. 11A, the insulating layer 25 of the pad portionand the insulating layer 3 on the interconnection layer 11 of the padportion are etched by using the photoresist 26 as the mask, therebyforming a contact hole which reaches the interconnection layer 11through these insulating layers 25, 3. At that time, since the openingof the photoresist 26 is smaller than the insulating layer 25 of the padportion, the insulating layer 25 is left around the contact hole,thereby forming the insulating layer 14 shown in FIG. 4.

After that, the photoresist 26 is removed as shown in FIG. 11B.

Next, as shown in FIG. 1C, a metal layer 27 serving as a material of acontact layer, for example, a W (tungsten) layer is formed on the wholesurface so as to bury the contact hole.

While W (tungsten) is used as the material that fills the contact holeas described above, the present invention is not limited thereto and Alor Cu or Ag or Au of alloy thereof may be used as the material forfilling the contact hole. Also, when the metal layer 27 is filled intothe contact hole, a barrier metal film may be formed on the underlayerin advance according to the need.

Next, as shown in FIG. 12A, a metal layer 27 is removed from the surfaceby the CMP method or the RIE method. As a result, the metal layer 27 isleft only within the contact hole to serve as a contact layer 12.

Next, as shown in FIG. 12B, a planarized layer 5 made of SiO₂, forexample, is deposited on the surface.

Next, as shown in FIG. 12C, a photoresist 28 is formed on the planarizedlayer 5. Further, the photoresist 28 is removed from only the padportion by exposing and developing the photoresist 28 as shown in FIG.13A.

Next, as shown in FIG. 13B, while the photoresist 28 is being used asthe mask, only the pad portion is removed by etching the planarizedlayer 5, whereby the contact layer 12 is exposed.

Subsequently, as shown in FIG. 13C, the photoresist 28 is removed.

Next, as shown in FIG. 14A, an electrode layer 15 made of Al, forexample, is deposited on the whole surface.

Next, as shown in FIG. 14B, a photoresist 29 is formed on the surface.Further, the photoresist 29 is left in only the pad portion by exposingand developing the photoresist 29 as shown in FIG. 14C.

Next, as shown in FIG. 15A, while the photoresist 29 is being used as amask, the electrode 15 is left in only the pad portion by etching theelectrode layer 15. Subsequently, the photoresist 29 is removed as shownin FIG. 15B.

Next, as shown in FIG. 15C, a color filter 6 is formed on the planarizedlayer 5 formed above the photodiode PD of the image pickup region by awell-known method.

Subsequently, as shown in FIG. 16A, a coating film 30 is formed bycoating a material serving as an on-chip lens on the color filter 6.

Finally, an on-chip lens 7 whose surface is shaped as a curved surfaceis produced from the coating film 30 by a well-known method as shown inFIG. 16B. In this manner, the solid-state imaging device 1 shown in FIG.4 can be manufactured.

At that time, since the alignment mark is formed around the photodiodePD by the insulating layer 13, the photodiode PD and the on-chip lens 7can be formed without positional displacement.

While the on-chip lens 7 is formed after the electrode layer 15 wasformed in the above-mentioned manufacturing process, the electrode layer15 may be formed after the on-chip lens 7 was formed.

A manufacturing process in that case will be described next.

The manufacturing processes shown in FIGS. 6A to 12B are similar tothose of the manufacturing process of this case.

After the manufacturing process shown in FIG. 12B, the color filter 6 isformed on the planarized layer 5 formed above the photodiode PD as shownin FIG. 17A.

Subsequently, as shown in FIG. 17B, the coating film 30 is formed bycoating the material serving as the on-chip lens on the color filter 6.

Next, the on-chip lens 7 whose surface is shaped as the curved surfaceis produced from the coating film 30 as shown in FIG. 17C.

At that time, since the alignment mark is formed around the photodiodePD by the insulating layer 13, the photodiode PD and the on-chip lens 7can be formed without positional displacement.

Next, as shown in FIG. 18A, a photoresist 31 is formed on the wholesurface. Further, the photoresist 31 is removed from only the padportion by exposing and developing the photoresist 31.

Next, as shown in FIG. 18C, while the photoresist 31 is being used asthe mask, only the pad portion is removed by etching the planarizedlayer 5. Subsequently, the photoresist 31 is removed as shown in FIG.19A.

Next, as shown in FIG. 19B, the electrode layer 15 is deposited on thewhole surface.

Next, as shown in FIG. 19C, the photoresist 32 is formed on the surface.Further, the photoresist 32 is left in only the pad portion by exposingand developing the photoresist 32 as shown in FIG. 20A.

Next, as shown in FIG. 20B, while the photoresist 32 is being used asthe mask, the electrode layer 15 is left only in the pad portion byetching the electrode layer 15. Subsequently, the photoresist 32 isremoved as shown in FIG. 20C.

In this manner, the solid-state imaging device 1 shown in FIG. 4 can bemanufactured.

According to the above-mentioned manufacturing process, the photodiodePD and the on-chip lens 7 can be formed without positional displacementby using the insulating layer as the alignment mark. Also, the padportion can be formed by the electrode layer 15 and hence the CMOS typesolid-state imaging device with the back-illuminated type structure canbe manufactured.

Further, while the solid-state imaging device 1 is manufactured from thesilicon substrate 21 in any one of the above-mentioned respectivemanufacturing processes, the present invention is not limited theretoand a solid-state imaging device may be formed from an SOI(silicon-on-insulator) substrate. A manufacturing process in that casewill be described next.

First, there is prepared an SOI substrate 36 comprising a siliconsubstrate 33, an SiO₂ film (silicon oxide film) 34 and a silicon layer35. As shown in FIG. 21A, a thin oxide film 22 is formed by oxidizingthe upper surface of the silicon layer 35 of this SOI substrate 36.

Next, as shown in FIG. 21B, an SiN film 23 and a photoresist 24 aredeposited on the oxide film 22, in that order.

Next, as shown in FIG. 21C, a through-hole is formed by exposing anddeveloping the photoresist 24.

Next, as shown in FIG. 22A, while the photoresist 24 is being used as amask, a through-hole is formed on the SiN film 23 by etching. Further,as shown in FIG. 22B, the SiN film 23 is left by removing thephotoresist 24, whereby a hard mask (SiN film 23) for etching thesilicon layer 35 is formed.

Next, as shown in FIG. 22C, an alignment mark groove and a pad contacthole (having depths ranging from approximately 5 to 20 μm) are formed onthe silicon layer 35 by the RIE method, thereby forming a contact holewhich reaches the SiO₂ film 34. A film thickness of the silicon layer 35is selected in advance in such a manner that the depth of the contacthole formed at that time may correspond to the depth of the photodiodePD which will be formed later on.

Next, as shown in FIG. 23A, an insulating layer 25 made of SiO₂, forexample, is formed on the whole surface so as to fill the groove formedon the silicon layer 35. A material of the insulating layer 25 to befilled may be a suitable material such as SiN and any material can beused so long as the material is the insulating material.

Next, as shown in FIG. 23B, the insulating layer 25 is removed from thesurface by the CMP method or the RIE method, whereby the insulatinglayer 25 is left within only the groove and the contact hole.

Next, after the SiN film 23 was removed, as shown in FIG. 23C, animpurity region comprising the photodiode PD of the light-receivingsensor portion is formed within the silicon layer 35. At that time, theinsulating layer 25 buried into the portion corresponding to theperipheral portion of the image pickup region 20 has a reflectivitydifferent from that of the surrounding silicon layer 21 and the surfaceof this insulating layer 25 is protruded, the photodiode PD can beproperly aligned by using this insulating layer 25.

Then, as shown in FIG. 24A, the interconnection layers 4 of multilayerare deposited on the silicon layer 35 through the insulating layer 3sequentially, thereby forming an interconnection portion.

After that, the SiO₂ film (adhesive layer) 9 is formed on the surface ofthe insulating layer 3 and the surface thereof is planarized andpolished. At the same time, the supporting substrate 8 with the T-SiO₂film (adhesive layer) formed on its surface is prepared, and theinsulating layer 3 of the interconnection portion and the supportingsubstrate 8 are bonded together as shown in FIG. 24C in such a mannerthat the SiO₂ films 9, 10 may be opposed to each other as shown in FIG.24B.

Next, as shown in FIG. 25A, the wafer is inverted up and down.

Next, the silicon layer 35 and the insulating layer 25 within thepreviously-formed groove and contact hole are exposed by removing thesilicon layer 35, the SiO₂ film (silicon oxide film) 34 serving as theback material of the wafer in accordance with the CMP method, RIEmethod, the BGR method or the combination of these three methods. As aresult, the insulating layer 13 of the alignment mark is formed from theinsulating layer 25. Also, the insulating layer 25 of the pad portionbecomes the insulating layer 14 formed around the contact layer.

After that, through the processes shown in FIGS. 10C to 16B, thesolid-state imaging device 1 shown in FIG. 4 can be manufactured.

According to the above-mentioned solid-state imaging device 1 of thisembodiment, since the insulating layer 13 is buried around the imagepickup region 20 through the silicon layer 2, when the solid-stateimaging device 1 is manufactured, it becomes possible to align thephotodiode PD of the light-receiving sensor portion and the on-chip lens7 by using this insulating layer 13 as the alignment mark (that is, markfor use as alignment). Thus, it becomes possible to accurately form theon-chip lens 7 at the predetermined position in alignment with thephotodiode PD.

Also, in the pad portion, the contact layer 12 is formed within theinsulating layer 14 buried into the silicon layer 2 while it is beingconnected to the interconnection layer 11 on the surface side of thesilicon layer 2, and the electrode layer 15 formed on the surface andthe interconnection layer 11 are connected through this contact layer12. As a result, the insulating layer 14 insulates the silicon layer 2and the contact layer 12 and the pad portion is constructed by theelectrode layer 15.

Then, if the photodiode PD of the light-receiving sensor portion isformed after the insulating layer 13 was buried into the silicon layer2, then the photodiode PD can be accurately formed at the predeterminedposition by using the insulating layer 13 as the alignment mark.

Also, if the contact hole is formed within the insulating layer 14 afterthe insulating layer 14 was buried into the silicon layer 2 of the padportion and the conductive material is buried into this contact hole soas to be connected to the interconnection layer 1, then the contactlayer 12 for connecting the interconnection layer 11 and the electrodelayer 15 can be formed and the silicon layer 2 and the contact layer 12can be insulated from each other by the insulating layer 14.

Therefore, according to this embodiment, since it becomes possible toform the alignment mark for aligning the photodiode PD of thelight-receiving sensor portion and the on-chip lens 7 and the padportion, it becomes possible to realize the solid-state imaging devicewith the back-illuminated type structure.

Thus, it becomes possible to achieve the effective vignetting factor of100% of slanting incident light by the back-illuminated type structureand sensitivity can be improved considerably. Therefore, it becomespossible to realize the solid-state imaging device which is free fromthe shading.

FIG. 26 is a schematic diagram (cross-sectional view) showing anarrangement of a solid-state imaging device according to otherembodiment of the present invention.

As shown in FIG. 26, in particular, around the image pickup region 20, asecond silicon layer (for example, amorphous silicon layer orpolycrystalline silicon layer) 17 is buried into the first silicon layer(single crystal silicon layer) 2 in which the photodiode PD is formed.Further, a metal layer 16 is formed on an insulating layer 19 on thissecond silicon layer 17.

Further, also in the pad portion, a second silicon layer 18 is buriedinstead of the insulating layer 14 shown in FIG. 4. Then, an insulatinglayer 19 is deposited between the contact layer 12 and the secondsilicon layer 18 in order to insulate the contact layer 12 forconnecting the interconnection layer 11 and the electrode layer 15 andthe buried second silicon layer 18.

While the insulating layer 19 can be made of the same insulatingmaterial as that of the planarized layer 5 shown in FIG. 4, theinsulating layer 19 is formed by a method different from that of theplanarized layer 5.

In this case, since the metal layer 16 and the insulating layer 19 aredifferent from each other in reflectivity of light, the metal layer 16is used as the alignment mark which can align the photodiode PD and theon-chip lens 7.

A rest of arrangement is similar to that of the solid-state imagingdevice according to the preceding embodiment. Hence, identical elementsand parts are denoted by the identical reference numerals and thereforeneed not be described in detail.

A solid-state imaging device according to this embodiment can bemanufactured as follows, for example.

A process flowchart required before the contact hole of the pad portionis formed is similar to that for manufacturing the solid-state imagingdevice 1 according to the preceding embodiment and differs only in thatthe insulating layers 13, 14 are changed to the second silicon layers17, 18. Although not shown, when the photodiode PD is manufactured,since the surface of the second silicon layer 17 buried around the imagepickup region 20 is protruded, it is possible to align the photodiode PDby using this second silicon layer 17.

Let us start describing the manufacturing process for manufacturing thesolid-state imaging device 110 in the state in which the contact hole ofthe pad portion is formed, which corresponds to the state shown in FIG.11B.

As shown in FIG. 27A, around the image pickup region 20 (see FIG. 26),the second silicon layer 17 is buried into the first silicon layer 2 inwhich the photodiode PD is formed, and an insulating layer 37 isdeposited on the whole surface so as to fill the contact hole from thestate in which the second silicon layer 18 is buried around the contacthole.

Next, as shown in FIG. 27B, a photoresist 38 is formed on the surface.Further, as shown in FIG. 27C, a through-hole is formed on a photoresist38 by exposing and developing the photoresist 38. At that time, athrough-hole is formed on the alignment mark portion.

Next, as shown in FIG. 28A, the insulating layer 37 is etched by usingthe photoresist 38 as the mask, whereby a groove which reaches theinterconnection layer is formed on the pad portion and a groove is alsoformed on the alignment mark portion. Thereafter, the photoresist 38 isremoved as shown in FIG. 28B.

Next, as shown in FIG. 28C, a metal layer 39 made of a suitable materialsuch as W (tungsten) is formed on the whole surface so as to fill thethrough-hole of the pad portion and the groove of the alignment markportion. When the metal layer 39 is filled into the contact hole, abarrier metal film may be formed on the underlayer in advance accordingto the need.

Then, as shown in FIG. 29A, the metal layer 39 is removed from thesurface, whereby the metal layer 39 is left in only the through-hole ofthe pad portion and in the groove of the alignment mark portion. Themetal layer 39 within the groove of the pad portion becomes the contactlayer 12 and the metal layer 39 within the groove of the alignment markportion becomes the metal layer 16 of the alignment mark. The contactlayer 12 and the second silicon layer 12 are insulated from each otherby an insulating layer 37 (which becomes the insulating layer 19 shownin FIG. 4) buried between the contact layer 12 and the second siliconlayer 18.

Next, as shown in FIG. 29B, the electrode layer 15 is deposited on thesurface.

After that, through the processes similar to those shown in FIGS. 14B to16B, the solid-state imaging device 110 shown in FIG. 26 can bemanufactured.

According to the above-mentioned manufacturing process, the photodiodePD and the on-chip lens 7 can be formed without positional displacementby using the metal layer 16 as the alignment mark. Also, it becomespossible to form the pad portion by the electrode layer 15 and the CMOStype solid-state imaging device with the back-illuminated type structurecan be manufactured.

While the silicon substrate 21 is used in the above-mentionedmanufacturing method, it is possible to manufacture the solid-stateimaging device 110 shown in FIG. 26 by using the SOI substrate shown inFIG. 21A. Also in that case, the fundamental process flow will not bechanged. The silicon layer 35 of the SOI substrate 36 becomes the firstsilicon layer 2 according to this embodiment.

Further, according to this embodiment, the second silicon layers 17, 18are filled into the grooves, the filling material, which is not only thenitride film but the oxide film, has an etching selection property andhence it becomes possible to use the oxide film instead of the SiN film23 shown in FIGS. 6B to 8B.

According to the solid-state imaging device 110 of this embodiment,since the second silicon layer 17 is formed around the image pickupregion 20 through the first silicon layer 2 and the metal layer 16 isformed on the second silicon layer 17, when the solid-state imagingdevice 110 is manufactured, it becomes possible to align the photodiodePD of the light-receiving sensor portion and the on-chip lens 7 by usingthis metal layer 16 as the alignment mark (that is, mark for alignment).As a result, it becomes possible to accurately form the on-chip lens 7at the predetermined position in alignment with the photodiode PD.

Also, in the pad portion, the contact layer 12 is formed within thesecond silicon layer 18 buried in to the first silicon layer 2 throughthe insulating layer 19 so as to be connected to the interconnectionlayer 11 on the surface side of the first silicon layer 2 and theelectrode layer 15 formed on the surface and the interconnection layer11 are connected. Thus, the second silicon layer 18 and the contactlayer 12 are insulated from each other by the insulating layer 19 andthe pad portion is constructed by the electrode layer 15.

Then, if the photodiode PD of the light-receiving sensor portion isformed after the second silicon layer 17 was buried into the firstsilicon layer 2, then the photodiode PD can be accurately formed at thepredetermined position by using the second silicon layer 17 as thealignment mark.

Also, after the second silicon layer 18 was buried into the firstsilicon layer 2 of the pad portion, the insulating layer 19 is buriedinto the second silicon layer 18, the contact hole is formed within thisinsulating layer 19 and the conductive material is buried into thecontact hole and connected to the interconnection layer 11, whereby thecontact layer 12 for connecting the interconnection layer 11 and theelectrode layer 15 can be formed and the second silicon layer 18 and thecontact layer 12 can be insulated by the insulating layer 19.

Therefore, according to this embodiment, in the solid-state imagingdevice with the back-illuminated type structure, since it becomespossible to form the alignment mark for aligning the photodiode PD ofthe light-receiving sensor portion and the on-chip lens 7 and the padportion, it becomes possible to realize the solid-state imaging devicewith the back-illuminated type structure.

As a consequence, it becomes possible to achieve 100% of effectivevignetting factor of slanting incident light by the back-illuminatedtype structure. Hence, sensitivity can be improved considerably and itbecomes possible to realize the solid-state imaging device which is freefrom the shading.

While the groove for the alignment mark and the contact hole of the padportion are formed simultaneously as shown in FIG. 17C in themanufacturing processes shown in FIGS. 6A to 16B, the groove for thealignment mark and the contact hole of the pad portion can be formedseparately.

The manufacturing process in which the groove for the alignment mark andthe contact hole of the pad portion are formed separately will bedescribed below.

In this case, since the alignment mark is formed first and the contacthole of the pad portion is formed later on, in the same stage shown inFIG. 10B, the insulating layer 25 of the contact hole is not provided asshown in FIG. 30A and a rest of the arrangement is the same as thatshown in FIG. 10B.

Subsequently, a photoresist 40 is formed on the surface, and athrough-hole is formed on the photoresist 40 of the pad portion byexposing and developing the photoresist 40 as shown in FIG. 30B.

Next, while the photoresist 40 is being used as a mask, a recess portion(contact hole) that reaches the insulating layer 3 of theinterconnection portion is formed by etching the silicon layer 2. Afterthat, the photoresist 40 is removed as shown in FIG. 30C.

Next, as shown in FIG. 31B, an SiO₂ layer 41 is deposited on the wholesurface so as to fill the recess portion.

Thereafter, as shown in FIG. 31B, the SiO₂ layer 41 is removed from thesurface by the CMP method or the RIE method. As a result, the SiO₂ layer41 is left in only the recess portion, and this state becomessubstantially the same as shown in FIG. 10B.

When the groove of the alignment mark and the contact hole of the padportion are formed separately as described above, there is an advantagein which the materials buried into the groove for the alignment mark andthe contact hole can be made different so that optimum materials can beselected.

Further, when the solid-state imaging device 110 shown in FIG. 26 ismanufactured, the process for forming the groove in the first siliconlayer and the process for burying the second silicon layer into thegroove can be executed around the image pickup region and at the padportion either simultaneously or separately. Further, the photodiode PDcan be formed after the second silicon layer was buried around the imagepickup region, whereafter the second silicon layer can be buried intothe pad portion.

FIG. 32 is a schematic diagram (cross-sectional view) showing anarrangement of a solid-state imaging device according to a furtherembodiment of the present invention. In this embodiment, the solid-stateimaging device has an arrangement in which a contact layer of a padportion and an electrode layer are formed of dual damascene.

As shown in FIG. 32, an electrode layer 15 having a T-like cross-sectionis formed so as to be connected to an interconnection layer 11, inparticular, in the pad portion. The electrode layer 15 is composed of ahorizontal-direction portion 15A serving as a pad and anvertical-direction portion 15B that corresponds to the contact layer. Aplanarized layer 5 has a through-hole above the electrode layer 15.Also, an insulating layer 14 is formed to be wide as compared with thatof the solid-state imaging device 1 shown in FIG. 4.

A rest of arrangement is similar to that of the solid-state imagingdevice shown in FIG. 4. Hence, identical elements and parts are denotedby the identical reference numerals and need not be described in detail.

The solid-state imaging device 120 according to this embodiment can bemanufactured as follows.

FIG. 33A shows the same state as that of FIG. 10C. Also in this case,although the solid-state imaging device 120 is manufactured through theprocesses similar to those shown in FIGS. 6A to 10C, since an insulatinglayer 25 within a groove (first groove) formed on the pad portion has apad portion formed in the inside thereof, it is formed to besufficiently larger than a through-hole of a resist mask 26 for forminga contact.

Next, as shown in FIG. 33B, while the photoresist 26 is being used as amask, a contact hole (second groove) which reaches a pad interconnectionlayer 11 through these insulating layers 25, 3 is formed by etching theinsulating layer 25 of the pad portion and the insulating layer 3 on theinterconnection layer 11 of the pad portion according to the RIE method.At that time, since the through-hole of the photoresist 26 issufficiently smaller than the insulating layer 25 of the pad portion,the insulating layer 25 is left around the contact hole.

Subsequently, as shown in FIG. 33C, the photoresist 26 is removed.

Next, as shown in FIG. 34A, a photoresist 42 is formed on the wholesurface so as to fill the contact hole (second groove). Then, athrough-hole is formed on a photoresist 42 of a pad portion by exposingand developing the photoresist 42 as shown in FIG. 34B. At that time,the size of the through-hole is larger than the contact hole (secondgroove) and is also smaller than the insulating layer 25.

Next, as shown in FIG. 34C, the insulating layer 25 is partly etched byusing the photoresist 42 as a mask. At that time, part of thephotoresist 42 within the contact hole also is removed, whereby a groove(third groove) for use with a pad and which is narrower than the contacthole (second groove) is formed.

Subsequently, as shown in FIG. 35A, the photoresist 42 is removed.

Next, as shown in FIG. 35B, a metal layer 27 serving as the material ofthe contact layer, for example, W (tungsten) layer is formed on thewhole surface so as to fill the contact hole and the groove (thirdgroove) for the pad. Also, when the metal layer 27 is formed on thewhole surface so as to fill the contact hole, a barrier metal layer maybe formed on the underlayer in advance according to the need.

Then, as shown in FIG. 35C, the metal layer 27 is removed from thesurface by the CMP method of the RIE method. As a result, the metallayer 27 is left within only the contact hole and the groove (thirdgroove) for the pad and thereby the electrode layer 15 having the T-likecross-section composed of the horizontal-direction portion 15A servingas the pad and the vertical-direction portion 15B is formed.

Next, as shown kin FIG. 36A, the planarized layer 5 and a photoresist 43are formed on the surface, in that order. Then, as shown in FIG. 36B, athrough-hole is formed on the photoresist 43 above the electrode layer15 of the pad portion by exposing and developing the photoresist 43.

Next, after the planarized layer 5 was etched away by using thephotoresist 43, the photoresist 43 is removed as shown in FIG. 36C,whereby the planarized layer 5 is removed from the electrode layer 15 ofthe pad portion to expose the electrode layer 15 to the surface.

Thereafter, through the processes similar to those shown in FIGS. 15C to16B, respective assemblies up to the on-chip lens 7 are formed and thesolid-state imaging device 120 shown in FIG. 32 can be manufactured.

According to the above-mentioned manufacturing process, the photodiodePD and the on-chip lens 7 can be formed without positional displacementby using the insulating layer 13 as the alignment mark. Also, it becomespossible to form the pad by the electrode layer 15 and hence the CMOStype solid-state imaging device with the back-illuminated type structurecan be manufactured.

According to the above-mentioned solid-state imaging device 120 of thisembodiment, similarly to the solid-state imaging device 1 according tothe preceding embodiment, in the solid-state imaging device with theback-illuminated type structure, since the alignment mark for aligningthe photodiode PD of the light-receiving sensor portion and the on-chiplens 7 and the pad can be formed, it becomes possible to realize thesolid-state imaging device with the back-illuminated type structure.

As a result, it becomes possible to achieve the 100% of effectivevignetting factor of slanting incident light by the back-illuminatedtype structure. Thus, sensitivity can be improved considerably, andhence it becomes possible to realize the solid-state imaging devicewhich is free from the shading.

Also, in the solid-state imaging device 120 according to thisembodiment, since the electrode layer 15 having the T-like cross-sectionis formed so as to be connected to the interconnection layer 11, inparticular, in the pad portion, it becomes possible to form the contactlayer and the electrode layer by the same process at the same time.Thus, it becomes possible to suppress the number of processes in theprocess for forming the contact layer. Further, since the contact layerand the electrode layer can be made of the same material at the sametime, there is an advantage in which a contact resistance is notproduced between the contact layer and the electrode layer.

While the insulating layer 13 and the metal layer 16 used as thealignment marks are left in the solid-state imaging devices 1, 110 and120 according to the above-mentioned respective embodiments of thepresent invention, when an alignment mark is formed near the boundarybetween the adjacent chips 101 shown in FIG. 5A, if the wafer 100 isdivided into the chips 101 by a suitable method such as dicing, then thealignment mark will be sometimes removed partly or wholly.

Furthermore, while the present invention is applied to the solid-stateimaging device with the back-illuminated type structure according to theabove-mentioned respective embodiments, the present invention is notlimited thereto and can be similarly applied to a solid-state imagingdevice having other arrangement with a back-illuminated type structure.

For example, in a CCD (charge-coupled device) solid-state imaging devicewith a back-illuminated type structure or the like, it is possible toform an alignment mark and an electrode of a pad with application of thepresent invention.

According to the present invention, there is provided a solid-stateimaging device including a structure comprising at least a silicon layerin which a light-receiving sensor portion for effectingphotoelectric-conversion is formed, an interconnection layer formed onthe surface side of this silicon layer and in which a lens is formed onthe rear side opposite to the surface side of the silicon layer, aninsulating layer being buried into the silicon layer around an imagepickup region, the insulating layer being buried around a contact layerfor connecting an electrode layer of a pad portion and theinterconnection layer of the surface side.

According to the above-mentioned arrangement of the solid-state imagingdevice of the present invention, since this solid-state imaging deviceincludes the structure comprising at least the silicon layer in whichthe light-receiving sensor portion for effectingphotoelectric-conversion is formed and the interconnection layer formedon the surface side of this silicon layer and in which the lens isformed on the back side opposite to the surface side of the siliconlayer, the solid-state imaging device having the so-calledback-illuminated type structure is constructed in which the lens isformed on the rear side opposite to the surface side of the siliconlayer.

Then, since the insulating layer is buried into the silicon layer aroundthe image pickup region, when the solid-state imaging device ismanufactured, it becomes possible to align the light-receiving sensorportion and the lens by using this insulating layer as the alignmentmark.

Also, since the insulating layer is buried around the contact layer forconnecting the electrode layer of the pad portion and theinterconnection layer of the surface side, the contact layer and thesilicon layer can be insulated from each other by the insulating layerand the pad portion can be constructed by connecting the electrode layerto the interconnection layer of the surface side through the contactlayer.

According to the present invention, there is provided a solid-stateimaging device including a structure comprising at least a first siliconlayer in which a light-receiving sensor portion for effectingphotoelectric-conversion is formed and which is formed of a singlecrystal silicon layer, an interconnection layer formed on the surfaceside of this first silicon layer and in which a lens is formed on theback side opposite to the surface side of the first silicon layer, asecond silicon layer formed of an amorphous silicon layer or apolycrystalline silicon layer is buried into the first silicon layeraround an image pickup region, an insulating layer is formed on thefirst silicon layer, a metal layer is buried into the insulating layerat its portion above the second silicon layer, the insulating layer isburied around a contact layer for connecting an electrode layer of a padportion and an interconnection layer of the surface side and the secondsilicon layer is buried around the insulating layer.

According to the above-mentioned arrangement of the solid-state imagingdevice of the present invention, since this solid-state imaging devicehas the structure comprising at least the first silicon layer in whichthe light-receiving sensor portion for effectingphotoelectric-conversion is formed and the interconnection layer formedon the surface side of the first silicon layer and in which the lens isformed on the back side opposite to the surface side of the firstsilicon layer, the solid-state imaging device having the so-calledback-illuminated type structure is constructed in which the lens isformed on the back side opposite to the surface side of the firstsilicon layer.

Then, since the second silicon layer formed of the amorphous siliconlayer or the polycrystalline silicon layer is buried into the firstsilicon layer around the image pickup region, the insulating layer isformed on the first silicon layer and the metal layer is buried into theinsulating layer at its portion above the second silicon layer, when thesolid-state imaging device is manufactured, it becomes possible to alignthe light-receiving sensor portion and the lens by using this metallayer as the alignment mark.

Also, since the insulating layer that is formed on the first siliconlayer is buried around the contact layer for connecting the electrodelayer of the pad portion and the interconnection layer of the surfaceside and the second silicon layer is buried around the insulating layer,the contact layer, the second silicon layer and the first silicon layercan be insulated from one another by the insulating layer, and the padportion can be constructed by connecting the electrode layer to theinterconnection layer of the surface side through the contact layer.

According to the present invention, a method of manufacturing asolid-state imaging device is a method of manufacturing a solid-stateimaging device for manufacturing a solid-state imaging device includinga structure comprising a silicon layer in which a light-receiving sensorportion for effecting photoelectric-conversion is formed and aninterconnection layer formed on the surface side of this silicon layerand in which a lens is formed on the rear side opposite to the surfaceside of the silicon layer. This method of manufacturing a solid-stateimaging device comprises the steps of a process for forming a groove ona silicon layer around an image pickup region, a process for forming agroove on a silicon layer of a pad portion, a process for burying aninsulating layer into the groove formed around the image pickup region,a process for burying the insulating layer into the groove formed on thepad portion, a process for forming the light-receiving sensor portion onthe silicon layer after the insulating layer was buried around at leastthe image pickup region, a process for forming an interconnection layeron the surface side of the silicon layer, a process for connecting anelectrode layer to the interconnection layer of the pad portion byburying a conductive material into the insulating layer buried into thegroove of the pad portion and a process for forming a lens on the rearside of the silicon layer by using the insulating layer buried into thegroove around the image pickup region as an alignment mark.

According to the above-mentioned method of manufacturing a solid-stateimaging device of the present invention, there can be manufactured thesolid-state imaging device including the structure comprising at leastthe silicon layer in which the light-receiving sensor portion foreffecting photoelectric-conversion is formed and the interconnectionlayer formed on the surface side of this silicon layer and in which thelens is formed on the back side opposite to the surface side of thesilicon layer, that is, the solid-state imaging device having theso-called back-illuminated type structure.

Then, according to the above-mentioned method of manufacturing asolid-state imaging device of the present invention, since thismanufacturing method comprises the process for forming the groove on thesilicon layer around the image, pickup region, the process for buryingthe insulating layer into the groove formed around the image pickupregion, the process for forming the interconnection layer on the surfaceside of the silicon layer, the process for forming the light-receivingsensor portion on the silicon layer after the insulating layer wasburied around at least the image pickup region and the process forforming the lens on the rear side of the silicon layer by using theinsulating layer buried into the groove around the image pickup regionas the alignment mark, it becomes possible to form the photodiode of thelight-receiving sensor portion at the accurate position by using theinsulating layer as the alignment mark and further it becomes possibleto align the lens at the accurate position relative to the photodiode ofthe light-receiving sensor portion and the like.

Also, according to the present invention, this method of manufacturing asolid-state imaging device comprises the process for forming the grooveon the silicon layer of the pad portion, the process for burying theinsulating layer into the groove formed at the pad portion and theprocess for connecting the electrode layer to the interconnection layerof the pad portion by burying the conductive material into theinsulating layer buried into the groove of the pad portion, theconductive material buried into the insulating layer is connected to theinterconnection layer of the pad portion and the conductive material andthe silicon layer are insulated from each other by the insulating layer.Thus, the pad electrode is formed by using the conductive material asthe contact layer, thereby making it possible to form the pad portion.

According to the above-mentioned method of manufacturing a solid-stateimaging device of the present invention, in the process for forming thegroove on the silicon layer around the image pickup region, the siliconlayer may be etched by using a silicon nitride layer as a mask, asilicon oxide layer may be buried into the groove as the insulatinglayer in the state in which the silicon nitride layer is left and thesilicon oxide layer may be left only within the groove by removing thesilicon oxide layer from the surface, whereafter the silicon oxide layermay be protruded on the surface by removing the silicon nitride layerand the light-receiving sensor portion may be formed on the siliconlayer.

In this case, it becomes possible to form the photodiode of thelight-receiving sensor portion and the like at the predeterminedposition by using the protruded silicon oxide layer as the alignmentmark.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, it is possible to execute theprocess for forming the groove on the silicon layer around the imagepickup region and the process for forming the groove on the siliconlayer of the pad portion at the same time. Also, the process for buryingthe insulating layer into the groove formed around the image pickupregion and the process for burying the insulating layer into the grooveformed on the pad portion can be executed at the same time.

In this case, since the groove forming process and the process forburying the insulating layer into the groove are simultaneously aroundthe image pickup region and the pad portion, it becomes possible todecrease the number of processes.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, it is further possible toseparately execute the process for forming the groove on the siliconlayer around the image pickup region, the process for burying theinsulating layer into the groove formed around the image pickup region,the process for forming the groove on the silicon layer of the padportion and the process for burying the insulating layer into the grooveformed on the pad portion.

In this case, since the groove forming process and the process forburying the insulating layer into the groove are separately executedaround the image pickup region and at the pad portion, it becomespossible to optimize the material of the insulating layer buried intothe groove and the method of forming the groove in consideration ofvarious characteristics such as burying property and an etching rate.

Furthermore, after the insulating layer was buried into the grooveformed around the image pickup region, the process for forming thelight-receiving sensor portion on the silicon layer can be executed,whereafter the groove can be formed on the silicon layer of the padportion and the insulating layer can be buried into this groove. In thiscase, it is possible to form the photodiode of the light-receivingsensor portion and the like with high accuracy by using the insulatinglayer buried into the groove formed around the image pickup region asthe alignment mark. Also, since the insulating layer buried into thegroove of the pad portion is not used as the alignment mark, thematerial of the insulating layer can be selected freely.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, further, a second groovenarrower than the width of the insulating layer and which reaches theinterconnection layer of the pad portion through the insulating layercan be formed on the insulating layer buried into the groove of the padportion, a third groove narrower than the width of the insulating layerand which is wider than the width of the second groove can be formed onthe upper portion of the second groove and then the electrode layer canbe connected to the interconnection layer of the pad portion by buryingthe conductive material into the second and third grooves.

In this case, the conductive material within the narrow second groovecan act as the contact layer and it becomes possible to use theconductive material buried into the wider third groove formed on theupper portion of the second groove as the pad electrode. As a result,the contact layer and the pad electrode can be formed at the same time.

A method of manufacturing a solid-state imaging device according to thepresent invention is a method of manufacturing a solid-state imagingdevice including a structure comprising at least a first silicon layerin which a light-receiving sensor portion for effectingphotoelectric-conversion is formed, an interconnection layer formed onthe surface side of this first silicon layer and a lens formed on therear side opposite to the surface side of the first silicon layer. Thissolid-state imaging device manufacturing method comprises a process forforming a groove on a first silicon layer around an image pickup region,a process for forming a groove on the first silicon layer of a padportion, a process for burying a second silicon layer made of amorphoussilicon or polycrystalline silicon into a groove formed around the imagepickup region, a process for burying the second silicon layer made ofamorphous silicon or polycrystalline silicon into the groove formed atthe pad portion, a process for forming a light-receiving sensor portionon the first silicon layer after the second silicon layer was buriedaround at least the image pickup region, a process for forming aninterconnection layer on the surface side of the first silicon layer, aprocess for connecting an electrode layer to the interconnection layerby burying a conductive material into the second silicon layer buriedinto the groove of the pad portion through an insulating layer and aprocess for forming the insulating layer over the first silicon layer,burying a metal layer into the insulating layer at its portion above thesecond silicon layer around the image pickup region and forming a lenson the rear side of the first silicon layer by using this metal layer asan alignment mark.

The above-mentioned method of manufacturing a solid-state imaging deviceaccording to the present invention is to manufacture a solid-stateimaging device including a structure comprising at least a first siliconlayer in which a light-receiving sensor portion for effectingphotoelectric-conversion is formed, an interconnection layer formed onthe surface side of this first silicon layer and a lens formed on theback side opposite to the surface side of the first silicon layer, thatis, a solid-state imaging device having a so-called back-illuminatedtype structure.

Then, according to the above-mentioned method of manufacturing asolid-state imaging device of the present invention, since thissolid-state imaging device manufacturing method comprises the processfor forming the groove on the first silicon layer around the imagepickup region, the process for burying the second silicon layer made ofthe amorphous silicon or polycrystalline silicon into the groove formedaround the image pickup region, the process for forming thelight-receiving sensor portion on the first silicon layer after thesecond silicon layer was buried around at least the image pickup region,the process for forming the interconnection layer on the surface side ofthe first silicon layer and the process for forming the insulating layerover the first silicon layer, burying the metal layer into theinsulating layer at its portion above the second silicon layer aroundthe image pickup region and forming the lens on the rear side of thefirst silicon layer by using this metal layer as the alignment mark, itbecomes possible to accurately align the photodiode of thelight-receiving sensor portion and the like at the predeterminedposition by using the second silicon layer around the image pickupregion as the alignment mark. Further, it becomes possible to form thelens with the accurate alignment relative to the photodiode of thelight-receiving sensor portion and the like by using the metal layerformed on the portion above the second silicon layer around the imagepickup region as the alignment mark.

Also, since the solid-state imaging device manufacturing methodaccording to the present invention comprises the process for forming thegroove on the first silicon layer of the pad portion, the process forburying the second silicon layer made of the amorphous silicon or thepolycrystalline silicon into the groove formed on the pad portion andthe process for connecting the conductive material to theinterconnection layer by burying the conductive material into the secondsilicon layer buried into the groove of the pad portion through theinsulating layer, the conductive material buried into the second siliconlayer through the insulating layer is connected to the interconnectionlayer of the pad portion and the conductive material and the secondsilicon layer are insulated from each other by the insulating layer. Inconsequence, the pad electrode can be formed by using the conductivematerial as the contact layer, thereby making it possible to form thepad portion.

In the above-mentioned method of manufacturing a solid state imagepickup device according to the present invention, further, the processfor forming the groove on the first silicon layer around the imagepickup region and the process for forming the groove on the firstsilicon layer of the pad portion can be executed at the same time. Also,the process for burying the second silicon layer into the groove formedaround the image pickup region and the process for burying the secondsilicon layer into the groove formed at the pad portion can be executedat the same time.

In this case, since the groove forming process and the process forburying the second silicon layer into the groove are executed around theimage pickup region and at the pad portion at the same time, it becomespossible to decrease the number of processes.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, further, the process forforming the first silicon layer around the image pickup region and theprocess for burying the second silicon layer into the groove formedaround the image pickup region and the process for forming the groove onthe first silicon layer of the pad portion and the process for buryingthe second silicon layer into the groove formed at the pad portion canbe executed separately.

In this case, since the groove forming process and the process forburying the second silicon layer into the groove are executed around theimage pickup region and at the pad portion separately, it becomespossible to optimize the material (amorphous silicon or polycrystallinesilicon) of the second silicon layer buried into the groove and theforming method in consideration of various characteristics such as aburying property and an etching rate.

Further, after the second silicon layer was buried into the grooveformed around the image pickup region, the light-receiving sensorportion can be formed on the first silicon layer, whereafter the groovecan be formed on the first silicon layer of the pad portion and thesecond silicon layer can be buried into this groove. In this case, itbecomes possible to form the photodiode of the light-receiving sensorportion and the like accurately by using the second silicon layer buriedinto the groove formed around the image pickup region as the alignmentmark. Also, since the second silicon layer buried into the groove of thepad portion is not used as the alignment mark, the material can beselected freely.

In the above-mentioned method of manufacturing a solid-state imagingdevice according to the present invention, further in the process forforming the groove on the first silicon layer around the image pickupregion, the first silicon layer may be etched by using the insulatinglayer as a mask, the second silicon layer may be buried into the groovein the state in which the insulating layer is left, the second siliconlayer may be left only within the groove by removing the second siliconlayer from the surface, the second silicon layer may be protruded on thesurface by removing the insulating layer and the light-receiving sensorportion may be formed on the first silicon layer.

In this case, it becomes possible to form the photodiode of thelight-receiving sensor portion and the like at the predeterminedposition by using the thus protruded second silicon layer as thealignment mark.

According to the above-mentioned present invention, it becomes possibleto align the light-receiving sensor portion (photodiode, etc.) and thelens by using the insulating layer buried into the groove around theimage pickup region or the second silicon layer buried into the groovearound the image pickup region and the metal layer formed on the secondsilicon layer as the alignment mark.

In consequence, also in the solid-state imaging device having theback-illuminated type structure, it becomes possible to align thelight-receiving sensor portion (photodiode, etc.) and the lens at thepredetermined position accurately.

Further, according to the present invention, it becomes possible to forma pad by connecting the electrode layer and the interconnection layerafter the contact layer was formed by connecting the interconnectionlayer formed on the surface side in the pad portion.

Thus, it becomes possible to form the pad in the solid-state imagingdevice having the back-illuminated type structure too.

Therefore, according to the present invention, it becomes possible torealize the solid-state imaging device having the back-illuminated typestructure. Also, it becomes possible to achieve an effective vignettingfactor of 100% of slanting incident light by the back-illuminated typestructure. Furthermore, it becomes possible to considerably improvesensitivity and to realize the solid-state imaging device having theback-illuminated type structure which is free from the shading.

Having described preferred embodiments of the invention with referenceto the accompanying drawings, it is to be understood that the inventionis not limited to those precise embodiments and that various changes andmodifications could be effected therein by one skilled in the artwithout departing from the spirit or scope of the invention as definedin the appended claims.

What is claimed is:
 1. A solid-state image pickup device comprising: aninsulating layer between a first semiconductor substrate and a secondsemiconductor substrate, the second semiconductor substrate is betweenan electrode layer and the insulating layer; an adhesive layer betweenthe insulating layer and the first semiconductor substrate; anelectrically-insulative planarized layer between an on-chip lens and alight-receiving sensor portion of the second semiconductor substrate,the second semiconductor substrate is between the insulating layer andthe planarized layer; an electrically-insulative alignment mark betweenthe planarized layer and the insulating layer, the insulating layer andthe planarized layer touch the alignment mark; and a metal layer betweenthe electrode layer and the insulating layer, the insulating layer andthe electrode layer touch the metal layer.
 2. A solid-state image pickupdevice according to claim 1, wherein the adhesive layer is a film of anoxide.
 3. A solid-state image pickup device according to claim 2,wherein the oxide is a silicon oxide.
 4. A solid-state image pickupdevice according to claim 1, wherein the alignment mark and the metallayer extend completely through the second semiconductor substrate andpartially into the insulating layer.
 5. A solid-state image pickupdevice according to claim 4, wherein a different portion of the secondsemiconductor substrate is between the metal layer and the alignmentmark.
 6. A solid-state image pickup device according to claim 1, whereinthe first semiconductor substrate is silicon.
 7. A solid-state imagepickup device according to claim 1, wherein the second semiconductorsubstrate is silicon.
 8. A solid-state image pickup device according toclaim 1, wherein the alignment mark is a silicon oxide.
 9. A solid-stateimage pickup device according to claim 1, wherein the insulating layeris an insulating material and the planarized layer is the insulatingmaterial.
 10. A solid-state image pickup device according to claim 1,wherein the electrode layer touches the planarized layer.
 11. Asolid-state image pickup device according to claim 1, wherein thelight-receiving sensor portion is configured to effectphotoelectric-conversion.
 12. A solid-state image pickup deviceaccording to claim 1, wherein a portion of the metal layer at theelectrode layer is wider than a portion of the metal layer at theinsulating layer.
 13. A solid-state image pickup device according toclaim 1, wherein a reflectivity of the alignment mark differs from areflectivity of the second semiconductor substrate.
 14. A solid-stateimage pickup device according to claim 1, further comprising: aninterconnection layer within the interlayer insulator.
 15. A solid-stateimage pickup device according to claim 14, wherein the metal layertouches the electrode layer and the interconnection layer.
 16. Asolid-state image pickup device according to claim 1, furthercomprising: a color filter between the light-receiving sensor portionand the on-chip lens.
 17. A solid-state image pickup device according toclaim 16, wherein the color filter is between the on-chip lens and theplanarized layer.
 18. A solid-state image pickup device according toclaim 1, further comprising: a different alignment mark within theinsulating layer.
 19. A solid-state image pickup device according toclaim 18, wherein the light-receiving sensor portion of the secondsemiconductor substrate is between the alignment mark and the differentalignment mark.
 20. A solid-state image pickup device according to claim18, wherein the different alignment mark extends completely through thesecond semiconductor substrate and terminates at a boundary between theplanarized layer and the second semiconductor substrate.
 21. Asolid-state image pickup device according to claim 18, wherein in a planview of the solid-state image pickup device, an image pickup region isbetween the alignment mark and the different alignment mark.